Thermometer having a diagnostic function

ABSTRACT

The present disclosure relates to a device for determining and/or monitoring the temperature of a medium, comprising a temperature sensor with a temperature-sensitive sensor element which is placed in electrical contact by means of at least a first connection line and a second connection line, wherein the first connection line is divided into a first section and a second section, wherein the first section which faces the sensor element is composed of a first material, and wherein the second section which faces away from the sensor element is composed of a second material which differs from the first material, wherein the second connection line is composed of the second material, and wherein the first section of the first connection line and at least one part of the second connection line form a first difference temperature sensor in the form of a thermocouple.

The invention relates to a device for determining and/or monitoring thetemperature of a medium.

Thermometers are known from the prior art in a great variety ofembodiments. Thus, there are thermometers which use the expansion of aliquid, a gas or a solid with a known coefficient of expansion in orderto measure temperature, or also others which relate the electricalconductivity of a material, or a quantity derived therefrom, to thetemperature, such as electrical resistance when using, for example,resistance elements, or the thermoelectric effect in the case ofthermocouples. On the other hand, radiation thermometers, in particularpyrometers, use the heat radiation of a substance to determine itstemperature. The underlying measurement principles have each beendescribed in a variety of publications.

In the case of a temperature sensor in the form of a resistance element,so-called thin-film and thick-film sensors and so-called thermistors(also referred to as NTC thermistors) have become known, among others.In the case of a thin-film sensor, in particular a resistancetemperature detector (RTD), for example, a sensor element provided withconnecting wires and mounted on a carrier substrate is used, wherein theback side of the carrier substrate usually has a metal coating. Assensor elements, so-called resistance elements, for example, in the formof platinum elements, are used, which among other things are alsocommercially available under the designations PT10, PT100, and PT1000.

In the case of temperature sensors in the form of thermocouples,however, the temperature is determined by a thermovoltage which arisesbetween the unilaterally connected thermo wires made of differentmaterials. Thermocouples according to the DIN standard IEC584, e.g.,thermocouples of type K, J, N, S, R, B, T, or E, are usually used astemperature sensors for temperature measurement. However, other pairs ofmaterials, in particular those with a measurable Seebeck effect, arealso possible.

The task of thermometers in process automation is to determine thetemperature of a medium, or of a process medium, reliably and asaccurately as possible. In practice, there is the problem that thetemperature sensor used in each case is separated from the medium by aplurality of thermal resistors. Such thermal resistors come about, forexample, as a result of the individual components of the thermometer andpossibly as a result of the container in which the medium is located,e.g., a reservoir or a pipeline. Frequently, the temperature sensor ispart of a so-called measuring insert which comprises a casing element,which surrounds a filler and the temperature sensor embedded therein. Inthis case, serial thermal resistors result, for example, as a result ofthe casing and the filler.

If the thermometer also comprises, for example, a protective tube,further serial thermal resistors arise as a result of the protectivetube itself, as well as the thermal coupling between the protective tubeand the measuring insert. The choice of the length of the protectivetube and of the measuring insert plays a decisive role in achieving athermal balance between the process medium and the environment or thethermometer. If the protective tube and/or the measuring insert are/istoo short, a temperature gradient may occur in the region of thetemperature sensor. Such a temperature gradient depends on the one handon the difference in the temperature of the medium or the processtemperature, as the case may be, and the ambient temperature. On theother hand, however, the thermal conductivities of the respectively usedcomponents of the thermometer, the thermal couplings between theindividual components and different process parameters, such as a flowrate of the process medium or the like, also play a decisive role.

A further cause of the occurrence of temperature gradients in the regionof the temperature sensor is the formation of deposition layers and/orcorrosion on the thermometer, e.g., on the protective tube or measuringinsert, in particular in the region of the temperature sensor. Theformation of deposits or the occurrence of corrosion leads to a change,in particular a deterioration, of the thermal coupling between themedium and the component of the thermometer respectively coming intocontact with the medium, e.g., the protective tube or casing element.

Due to such temperature gradients in the region of the temperaturesensor, considerable falsifications of measured values can occurindependently of the exact cause of the gradient.

In order to avoid such falsifications of measured values, determiningthe true temperature value using three equidistant temperature sensors(Klaus lrrgang, Lothar Michalowsky has become known, for example:Temperaturmesspraxis [Temperature Measurement Practice], ISBN-13:978380272204). However, this approach requires a comparatively complexconstruction and signal evaluation.

DE102014119593A1 discloses a thermometer that enables a temperaturegradient to be detected along the connection lines. A resistance elementin the so-called 4-conductor circuit is used as the temperature sensor.On one of the connecting wires, one piece of the connection line isreplaced by another material, so that a differential thermocouple isformed from this and a further connection line. As soon as a temperaturegradient occurs at the connecting wire consisting of two elements or twomaterials, a thermovoltage arises which gives information about thetemperature gradient along the connecting wires. However, thistemperature gradient only relates to the extension direction of theconnecting wires. No direct statements can be made about any temperaturegradients occurring directly in the region of the temperature sensor.

The object of the present invention is therefore to specify athermometer with the highest possible measurement performance, inparticular with high measuring accuracy.

The object is achieved by the device according to claim 1. Advantageousembodiments are respectively specified in the dependent claims.

The object underlying the invention is achieved by a device fordetermining and/or monitoring the temperature of a medium, comprising atemperature sensor having a temperature-sensitive sensor element, whichis electrically contacted via at least a first connection line and asecond connection line. The first connection line is divided into afirst section and a second section, wherein the first section whichfaces the sensor element consists of a first material, and wherein thesecond section which faces away from the sensor element consists of asecond material which differs from the first material, while the secondconnection line likewise consists of the second material. The firstsection of the first connection line and at least a part of the secondconnection line then form a first difference temperature sensor in theform of a thermocouple.

According to the invention, the first difference temperature sensor isin principle a heat flow sensor according to the thermoelectricprinciple, by means of which a temperature gradient or heat flow at thelocation of the temperature sensor can be detected. If a temperaturegradient occurs in the region of the temperature sensor, a measuredvalue falsification of the temperature values determined by means of thetemperature sensor occurs. In this case, a thermovoltage can be detectedby means of the first difference temperature sensor. Advantageously, thetemperature gradient can thus be detected directly at the location ofthe temperature sensor, i.e., at the location at which the temperatureis determined and/or monitored. On the one hand, the two first sectionsof the first and second connection lines can be directly connected toone another and jointly attached to the temperature sensor. In thiscase, a first temperature sensor in the form of a thermocouple isespecially suitable. It is also possible for the first and secondconnection lines to be attached separately to the temperature sensor. Inthe second case, the first sections of the first and second connectionlines can then be electrically connected to one another by means of thetemperature sensor, for example.

The two connection lines serve on the one hand for contacting thetemperature sensor. At least the first section of the first connectionline and at least a part of the second connection line simultaneouslyform the first difference temperature sensor by means of which a heatflow in the region of the temperature sensor can be detected.

In one embodiment, the temperature-sensitive sensor element of thetemperature sensor is a resistance element. Depending on the type anddesign of the resistance element, the first and second connection lines,or the first sections of the first and second connection lines, can thenbe attached, for example, directly to the resistance element or also toa substrate on which the resistance element is arranged. The contactingcan thus take place, for example, both via the sensor element and via asubstrate on which the sensor element is arranged. It is likewisepossible to arrange at least a partial region of at least one connectionline, in particular the first part of at least one of the connectionlines, on the substrate. In the case of an embodiment of the resistanceelement as a thin-film or thick-film sensor, the at least one partialregion, arranged on the substrate, of at least one of the connectionlines can then advantageously be produced together with the sensorelement in a thin-film or thick-film method.

In a further embodiment of the device, the second connection line isdivided into a first section facing the sensor element and a secondsection facing away from the sensor element. In this case, the firstdifference temperature sensor is formed by the first sections of thefirst and second connection lines. In contrast, the second sections ofthe first and second connection lines can be so-called extension wireswhich can be connected to the first sections of the two connectionlines.

A particularly preferred embodiment includes the first section of thefirst connection line and the first section of the second connectionline or at least the part of the second connection line beingdimensioned in such a way, in particular wherein a length, across-sectional area, and/or a material are/is selected in such a way,that values for a first heat flow through the first section of the firstconnection line and/or through the first connection line and for asecond heat flow through the first section of the second connectionline, the part of the second connection line and/or the secondconnection line are essentially equal.

By appropriately dimensioning the connection lines or sections of theconnection lines, the heat flows along the two connection lines beingessentially identical can be achieved. In this way, the falsification ofthe measured values by the first difference temperature sensor can besignificantly reduced. For example, the sections of the connection linesthat consist of the second material, in particular the second connectionline and the second section of the first connection line, can bedesigned identically, while the first section of the first connectionline is dimensioned appropriately. In the case of a division of thesecond connection line into a first and a second section, however, thefirst and second sections can, for example, also be dimensioneddifferently, while the second sections of the first and secondconnection lines are dimensioned identically. Many different variantsare conceivable in this respect, all of which fall within the presentinvention.

It is advantageous if the first section of the first connection line andthe first section of the second connection line have essentially thesame length. This especially allows the first sections of the connectionlines to be connected in a simple manner to the second sections formingthe extension wires.

A further preferred embodiment includes the device comprising at leastone third connection line for electrically contacting the temperaturesensor. Many different embodiments are conceivable here, all of whichfall within the present invention. Both the second and the thirdconnection line can, for example, form the first difference temperaturesensor with the first connection line. It is also conceivable to operatethe temperature sensor in a so-called two-conductor circuit orthree-conductor circuit.

With regard to an embodiment having three connection lines, it isadvantageous if the third connection line is divided into a firstsection facing the sensor element and into a second section facing awayfrom the sensor element, wherein the first section of the thirdconnection line consists of the first material and a third material,wherein the second section of the third connection line consists of thesecond material, and wherein the first section of the third connectionline and at least a part of the second connection line form a seconddifference temperature sensor in the form of a thermocouple. The seconddifference temperature sensor can then also be used for detecting a heatflow, in particular in the region of the temperature sensor. On the onehand, the first and second difference temperature sensors can bedesigned identically. However, it is also conceivable to design the twodifference temperature sensors differently. For this purpose, forexample, the first sections of the first and third connection lines canbe dimensioned differently, e.g., with regard to the length, the crosssection, or the material used in each case.

In a further particularly preferred embodiment, the device comprises atleast a fourth connection line for electrically contacting thetemperature sensor. Many different embodiments are also conceivable inthis respect, all of which fall within the present invention. Thesecond, the third or the fourth connection line can form the firstdifference temperature sensor with the first connection line, forexample. The same considerations apply to an optionally present seconddifference temperature sensor. It is also conceivable to operate thetemperature sensor in a so-called two-conductor, three-conductor, orfour-conductor circuit.

It is advantageous if the fourth connection line is/are divided into afirst section facing the sensor element and into a second section facingaway from the sensor element, wherein the first section of the fourthconnection line consists of the first, the third or a fourth material,wherein the second section of the fourth connection line consists of thesecond material, and wherein the first section of the fourth connectionline and at least a part of the second or the third connection line forma third difference temperature sensor in the form of a thermocouple. Thethird difference temperature sensor can then also be used for detectinga heat flow, in particular in the region of the temperature sensor. Onthe one hand, the first, second and/or third difference temperaturesensors can be designed identically. However, it is also conceivable todesign at least two of the at least three difference temperature sensorsdifferently. For this purpose, the first sections of the first, thirdand/or fourth connection lines can, for example, be dimensioneddifferently, e.g., with regard to the length, the cross section, or thematerial used in each case.

A preferred embodiment includes, for example, that a length of the firstsection of the third and/or the fourth connection line differs from thelength of the first section of the first connection line.

In one embodiment, the device according to the invention comprises anelectronics module which is designed to detect a first, a second and/ora third thermovoltage dropping at the first, the second and/or the thirddifference temperature sensor.

In this respect, it is advantageous if the electronics module isdesigned to determine a heat flow, in particular a heat dissipation, ofthe temperature sensor on the basis of the first, the second and/or thethird thermovoltage. If, for example, no thermovoltage arises at thefirst, the second and/or the third difference temperature sensor, it canbe concluded that no temperature gradient occurs in the region of thetemperature sensor. The falsification of a measured value obtained bymeans of the temperature sensor for the temperature of the medium due toheat flows in the region of the temperature sensor can accordingly beruled out.

It is also advantageous if the electronics module is designed to detecta deposit on a medium-contacting component of the thermometer, inparticular on a protective tube, on the basis of the first, the secondand/or the third thermovoltage. If deposits form on the thermometer incontinuous operation, this has a possibly considerable influence on thethermal properties of the thermometer, in particular on the thermalcoupling between the medium and the thermometer, and can thus be a causeof temperature gradients occurring in the region of the temperaturesensor.

It is furthermore advantageous if the electronics module is designed todetermine, on the basis of the first, second and/or thirdthermovoltages, a statement about a physical and/or chemical property ofthe medium, e.g., a flow rate, a flow velocity or a specific heatcapacity, or a heat transfer coefficient, a heat flow of the medium or achange in the composition of the medium. In this case as well, a changein one of these variables causes a change in the thermal couplingbetween medium and thermometer and can thus be a cause of a temperaturegradient occurring in the region of the temperature sensor.

The invention is explained in more detail based upon the followingdrawings. The following are shown:

FIG. 1: a schematic representation of a thermometer according to theprior art with a temperature sensor in the form of a resistance element,

FIG. 2: a schematic representation of a thermometer according to theinvention with two connection lines in different embodiments,

FIG. 3: a schematic representation of a thermometer according to theinvention with three connection lines in different embodiments, and

FIG. 4: a schematic representation of a thermometer according to theinvention with four connection lines in different embodiments.

In the figures, the same features are identified with the same referencesigns.

FIG. 1 shows a schematic representation of a thermometer 1 with adipping body 2, e.g., a protective tube, a measuring insert 3, and anelectronics module 4 according to the prior art. The measuring insert 3is introduced into the dipping body 2 and comprises a temperature sensor5 which in the present case comprises a temperature-sensitive element inthe form of a resistance element. The temperature sensor is electricallycontacted via the connection lines 6 and connected to the electronicsmodule 4. In other embodiments, the electronics module 4 can also bearranged separately from the measuring insert 3 and dipping body 2. Inaddition, the sensor element 5 need not necessarily be a resistanceelement, nor does the number of connection lines 6 used need necessarilybe two. Rather, the number of connection lines 6 can be selectedappropriately depending on the measurement principle used and thetemperature sensor used.

As already explained, the measuring accuracy of a thermometer 1 dependsto a large extent on the respective materials and on contacting means,in particular thermal contacting means, in particular in the region ofthe temperature sensor 5. The temperature sensor 5 is in thermal contactwith the medium M indirectly, i.e., via the dipping body 2. Thetemperature sensor 5 is thus separated from the medium M by a pluralityof thermal resistors. Depending on the process conditions and/or therespective structural design of the thermometer, no thermal equilibriumbetween the medium M and the thermometer may therefore be present atleast temporarily and/or in part. As a result of the absence of athermal equilibrium, temperature gradients ΔT₁ or ΔT₂ may arise, forexample, in the region of the temperature sensor 5 or also along theconnection lines 6, said temperature gradients falsifying thetemperature values measured in each case with the temperature sensor 5as a result of resulting heat flows.

Temperature gradients ΔT₁ in the region of the temperature sensor 5 areparticularly relevant in this context. The present invention thereforeenables the detection of such temperature gradients. This leads to asignificantly improved measuring accuracy of the thermometer.

A first embodiment of the thermometer according to the invention isshown in FIG. 2. A temperature sensor T₁ in the form of a resistanceelement 7 applied to a substrate 8 is used for determining and/ormonitoring the temperature T of the medium M. The temperature sensor T₁is electrically contacted by means of the two connection lines 9 and 10and is thus operated in the so-called two-conductor circuit. In thepresent case, both connection lines 9 and 10 are attached directly tothe resistance element 7. However, it should be noted at this point thatall the contacting means known to the person skilled in the art forconnecting the first temperature sensor T₁ to the connection lines 9 and10 are also possible and fall under the present invention.

The first connection line 9 is divided into a first section 9 a and asecond section 9 b. The first section 9 a consists of a first material,and the second section 9 b and the second connection line 10 consist ofa second material which differs from the first material. In this way,the first section 9 a of the first connection line 9 and at least a partt of the second connection line 10 form a first difference temperaturesensor T₂ in the form of a thermocouple. The two materials for the firstsection 9 a of the first connection line 9 and the second section 9 b ofthe first connection line and for the second connection line 10 areselected in such a way that a thermovoltage can be detected by means ofT₂ due to a temperature difference between the points a and b and thedifferent thermovoltages forming accordingly in the sections 9 a and tdue to the thermoelectric effect.

The first section 9 a of the first connection line 9 is preferably shortin comparison to the total length of the first connection line 9; forexample, the length of the first section 9 a of the first connectionline 9 is in the range of a few millimeters or centimeters. In this way,it can be ensured that the values determined by means of the firstdifference temperature sensor T₂ reflect a temperature gradient ΔT₁ inthe region of the temperature sensor T₁ as far as possible.

In the example shown in FIG. 2a , the first connection line 9 and thesecond connecting line 10 are separately attached to the resistanceelement. The first section 9 a of the first connection line 9 and thepart t of the second connection line 10 are thus indirectly connectedvia the resistance element 7. In another embodiment, however, the firstsection 9 a of the first connection line 9 and the part t of the secondconnection line 10 could also be connected directly to one another andthen attached to the temperature sensor T₁. Of course, instead of thetemperature sensor T₁ shown by way of example here for all figures witha sensor element in the form of a resistance element 7, othertemperature sensors well known to the person skilled in the art can alsobe used and also fall under the present invention.

In the embodiment shown in FIG. 2b , the second connection line 10 isalso divided into a first section 10 a and a second section 10 b. Inthis case, the first difference temperature sensor T₂ is formed by thefirst sections 9 a and 10 a of the first connection line 9 and thesecond connection line 10. According to FIG. 2b , but not necessarily,the two first sections 9 a and 10 a of the two connection lines 9 and 10are of the same length. In this case, the second sections 9 b and 10 bof the first connection line 9 and of the second connection line 10 areextension wires, preferably similarly designed extension wires. However,in the case of the embodiment according to FIG. 2a , it is alsoadvantageous if the second section 9 b of the first connection line 9and the second connection line 10 are of similar design.

FIG. 3 shows by way of example two different embodiments of a device 1according to the invention in which the temperature sensor T₁ isconnected by means of three connection lines 9-11. The two embodimentsshown are to be understood only as examples. There are numerousalternative embodiments of an arrangement according to the inventionwith three connection lines 9-11 which are likewise possible.

According to FIG. 3a , the temperature sensor T₁ is connected by meansof the three connection lines 9-11. Apart from the third connection line11, this embodiment corresponds to the variant shown in FIG. 2b .Elements already explained are therefore not discussed again at thispoint. By using three connection lines 9-11, the temperature sensor T₁can advantageously be operated in the so-called three-conductor circuit.The third connection line 11 for this embodiment preferably consists ofthe same material as the second connection line 10 and as the secondsection 9 b of the first connection line 9.

FIG. 3b shows another exemplary embodiment of a device 1 according tothe invention having three connection lines 9-11. In contrast to FIG. 3a, the first sections of the first connection line 9 a and of the secondconnection line 10 b which form the first difference temperature sensorT₂ are directly connected to one another. Moreover, the third connectionline 11 is also divided into a first section 11 a and a second section11 b. The material of the first section 11 a of the third connectionline 11 differs from the material of the first section 10 a of thesecond connection line 10 in such a way that it forms a seconddifference temperature sensor T₃, also in the form of a thermocouple.However, the second difference temperature sensor T₃ can also be formedanalogously to that shown in FIG. 2a without a division of the secondconnection line 10 into two sections 10 a and 10 b. In this case, thematerials of which the first sections 9 a and 11 a of the firstconnection line 9 and of the third connection line 11 may be bothidentical, i.e., also different.

Four different embodiments of a thermometer 1 according to theinvention, which are likewise to be understood as exemplary, with 4connection lines 9-12 are lastly shown in FIG. 4. The variant shown inFIG. 4a corresponds largely to the variant shown in FIG. 3a . Elementsalready explained are therefore also not discussed again here. Inaddition to FIG. 3a , the embodiment according to FIG. 4b comprises afourth connection line 12. By using four connection lines 9-12, thetemperature sensor T₁ can advantageously be operated in the so-calledfour-conductor circuit. The fourth connection line 12 for thisembodiment preferably consists of the same material as the secondconnection line 10 and the third connection line 11 and as the secondsection 9 b of the first connection line 9.

Another possible embodiment is shown in FIG. 4b . With regard to thefirst connection line 9 and the second connection line 10, thisembodiment corresponds to that shown in FIG. 3b . The fourth connectionline 12 here, just as other connection lines 9-11, is divided into afirst section 12 a and a second section 12 b. The third connection line11 and the fourth connection line 12 are designed analogously to thefirst connection line 9 and the second connection line 10, wherein thefirst sections 11 a and 12 a of the third connection line 11 and of thefourth connection line 12 form the second difference temperature sensorT₃. In other embodiments, the first differential temperature sensor T₂and the second differential temperature sensor T₃ may also be designedin accordance with the embodiments from FIG. 2a or 2 b.

For the embodiment according to FIG. 4b , it is assumed by way ofexample that the materials of the second section 9 b of the firstconnection line 9, of the second connection line 10, of the secondsection 11 a of the third connection line 11, and of the fourthconnection line 12 are identical, while the first sections 9 a and 11 aof the first connection line 9 and of the third connection line 9 and 11differ therefrom. In this case, the materials of the first sections 9 aand 11 a can again respectively be identical or different.

In principle, similarly to the case of FIG. 3, the first differencetemperature sensor T₂ and the second difference temperature sensor T₃can be designed identically or differently. For example, a differencebetween the first difference temperature sensor T₂ and the seconddifference temperature sensor T₃ may be achieved by a different lengthof the first sections 9 a and 10 a of the first connection line 9 and ofthe second connection line 10 and the first sections 11 a and 12 a ofthe third connection line 11 and the fourth connection line 12 as shownin FIG. 4c . A variation of the cross sections of the sections 9 a-12 ais likewise conceivable.

A further exemplary embodiment is the subject matter of FIG. 4d . Withregard to the first connection line 9 and the second connection line 10,this embodiment likewise corresponds to that shown in FIG. 3b . Thethird connection line 11 and the fourth connection line 12 are alsorespectively divided into two sections 11 a and 11 b and 12 a and 12 bbut separately connected to the resistance element 7. Such firstsections 9 a, 11 a and 12 a of the first connection line 9, the thirdconnection line 11 and the fourth connection line 12 are of differentlengths and each forms a first difference temperature sensor T₂, asecond difference temperature sensor T₃ and a third differencetemperature sensor T₄ with a part t of the second connection linecorresponding to the respective length of the first sections 9 a, 11 a,12 a.

For the embodiment in FIG. 4d , it is assumed by way of example that thematerials of the second sections 9 b, 11 b and 12 b of the firstconnection line 9, the third connection line 11 and the fourthconnection line 12 as well as of the second connection line 10 areidentical, while the first sections 9 a, 11 a and 12 a of the firstconnection line 9, the third connection line 11 and the fourthconnection line 12 differ therefrom. In this case, the materials of thefirst sections 9 a, 11 a and 12 a can again be identical or at leastpartially different in each case.

It is pointed out that the individual embodiments described inconnection with individual figures can be combined with one another asdesired, and numerous other embodiments of the present invention notshown here are likewise possible.

LIST OF REFERENCE SIGNS

1 Device

2 Dipping body

3 Measuring insert

4 Electronics module

5 Sensor element

6 Connecting wires

7 Resistance element

8 Substrate

9-12 First-fourth connection line

9 a-12 a First sections of the connection lines

9 b-12 b Second sections of the connection lines

M Medium

T Temperature

T₁-T₄ Temperature sensors

ΔT₁, ΔT₂ Temperature gradients

1-14. (canceled)
 15. A device for determining or monitoring thetemperature of a medium, comprising: a temperature sensor having atemperature-sensitive sensor element which is electrically contacted viaat least a first connection line and a second connection line, whereinthe first connection line is divided into a first section and a secondsection, wherein the first section which faces the sensor elementconsists of a first material, and wherein the second section which facesaway from the sensor element consists of a second material which differsfrom the first material, wherein the second connection line consists ofthe second material, and wherein the first section of the firstconnection line and at least a part of the second connection line form afirst difference temperature sensor in the form of a thermocouple. 16.The device of claim 15, wherein the temperature-sensitive sensor elementof the temperature sensor is a resistance element.
 17. The device ofclaim 15, wherein the second connection line is divided into a firstsection facing the sensor element and a second section facing away fromthe sensor element.
 18. The device of claim 15, wherein the firstsection of the first connection line and the first section of the secondconnection line or at least the part of the second connection line aredimensioned in such a way that values for a first heat flow through thefirst section of the first connection line or through the firstconnection line and for a second heat flow through the first section ofthe second connection line, the part of the second connection line orthe second connection line are equal.
 19. The device of claim 18,wherein the first section of the first connection line and the firstsection of the second connection line have the same length.
 20. Thedevice of claim 15, comprising at least a third connection line forelectrically contacting the temperature sensor.
 21. The device of claim20, wherein the third connection line is divided into a first sectionfacing the sensor element and into a second section facing away from thesensor element, wherein the first section of the third connection lineconsists of the first material or a third material, wherein the secondsection of the third connection line consists of the second material,and wherein the first section of the third connection line and at leasta part of the second connection line form a second differencetemperature sensor in the form of a thermocouple.
 22. The device ofclaim 15, comprising at least a fourth connection line for electricallycontacting the temperature sensor.
 23. The device of claim 15, whereinthe fourth connection line is divided into a first section facing thesensor element and into a second section facing away from the sensorelement, wherein the first section of the fourth connection lineconsists of the first material, the third material or a fourth material,wherein the second section of the fourth connection line consist of thesecond material, and wherein the first section of the fourth connectionline and at least a part of the second connection line or of the thirdconnection line form a third difference temperature sensor in the formof a thermocouple.
 24. The device of claim 23, wherein a length of thefirst section of the third connection line or of the fourth connectionline differs from the length of the first section of the firstconnection line.
 25. The device of claim 15, comprising an electronicsmodule designed to detect a first, a second or a third thermovoltagedropping at the first difference temperature sensor, the seconddifference temperature sensor or the third difference temperaturesensor.
 26. The device of claim 25, wherein the electronics module isdesigned to determine a heat flow of the temperature sensor on the basisof the first, the second or the third thermovoltage.
 27. The device ofclaim 25, wherein the electronics module is designed to detect a depositon a medium-contacting component of the thermometer on the basis of thefirst, the second or the third thermovoltage.
 28. The device of claim25, wherein the electronics module is designed to determine, on thebasis of the first, the second or the third thermovoltage, a statementabout a physical or chemical property of the medium.